Filtration, lysis and absorption of bacteria by mussels Choromytilus meridionalis collected under upwelling and downwelling conditions

Abstract

Choromytilus meridionalis Krauss is able to filter single bacterial cells from surrounding water, even at low bacterial concentrations (4,16 × 10⁶·mℓ⁻¹). Under upwelling conditions (cold), filtration of bacteria is only slightly more efficient than under downwelling conditions (warm). However, upwelling conditions correspond with a very much higher efficiency of incorporation of bacterial biomass into body tissues owing to the production of a bacteriolytic factor by the crystalline style of the mussel, which only happens during upwelling. During upwelling, the concentration of lytic factor rises to 3 100 units·mg⁻¹ style protein but falls to < 1 unit·mg⁻¹ during downwelling. The lytic factor cause lysis of a wide range of marine bacterial strains, those isolated from the water column being particularly sensitive. The lytic factor is stable at 80°C. It does not lyse Micrococcus luteus, Escherichia coli or Bacillus subtilis and is therefore not a true lysozyme.